Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Food Samples by LC-MS/MS

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) represent a class of highly stable fluorinated chemicals that accumulate in the environment and food chain. Their persistence and potential health risks, including bioaccumulation and long-term exposure effects, make reliable analytical methods for PFAS in food essential for regulatory monitoring and consumer safety.

Objectives and Article Overview

This work describes the development and validation of a rapid LC-MS/MS method capable of quantifying forty PFAS compounds in a carrot matrix. The study evaluates two solid-phase extraction (SPE) cartridges, optimizes a QuEChERS-based sample preparation flow, and assesses recovery, matrix effects, and concentration procedures.

Methodology and Sample Preparation

• Sample: 10 g of frozen, ground carrots homogenized by freeze grinding.
• Extraction: Adapted QuEChERS protocol with 10 mL acetonitrile, sodium chloride, trisodium citrate, disodium hydrogen citrate, and magnesium sulfate. A single centrifugation step separates extract.
• Purification: Comparison of InertSep MA-2 and EVOLUTE EXPRESS WAX SPE cartridges. Sequential washes with methanol/water mixtures (0–100%) and eluents containing formic acid or ammonia identify optimal conditions.

Used Instrumentation

• LC-MS/MS: Shimadzu LCMS-8050 coupled to Nexera X3 UHPLC.
• Column: Shim-pack Scepter C18 (100 × 2.0 mm, 1.9 µm). Delay column Shim-pack GIST C18 to minimize background.
• Mobile phases: A = ACN/water 5:95 with 2 mmol/L ammonium acetate; B = ACN; gradient 20→100% B over 12 min.
• Ionization: ESI negative mode; DL and interface 200 °C; heat block 300 °C.

Main Results and Discussion

• Recovery: Most PFAS achieved 70–120% recovery for both SPE cartridges. No significant performance difference between InertSep MA-2 and WAX.
• Elution profiles: Critical methanol concentrations identified for efficient washing (formic acid/methanol/water 1:400:600) and elution (28% ammonia/methanol/water 1:90/10).
• Concentration step: Nitrogen blow-down caused severe losses for eight PFAS; thus direct injection of purified eluate was recommended.
• Throughput: Fifteen-minute LC-MS analysis covering forty analytes with minimized matrix suppression by reducing injection volume.

Benefits and Practical Applications

• High throughput screening of PFAS in food matrices with robust quantification.
• Broad analyte coverage, enabling regulatory compliance testing and exposure assessment.
• Simplified sample preparation reducing glassware and processing time.

Future Trends and Possibilities

• Extension to other food and environmental matrices using similar SPE-LC-MS/MS workflows.
• Integration of isotope dilution standards and high-resolution mass spectrometry for improved accuracy and identification of emerging PFAS.
• Automation of QuEChERS and SPE steps to increase laboratory throughput and reproducibility.

Conclusion

The presented LC-MS/MS method delivers rapid, reliable quantification of forty PFAS in carrot samples with acceptable recoveries, minimal matrix effects, and no significant difference between two SPE cartridges. Avoiding concentration losses and optimizing injection volumes ensures robust results suitable for routine food safety monitoring.

Reference

• EPA. Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS, 2nd Draft Method 1633, June 2022.